Gas filling system, and vehicle

ABSTRACT

A vehicle includes: a fuel tank into which gas is filled from a gas station that has a receiver; a transmitter; and a control device connected to the transmitter. The control device changes a transmission cycle of a signal transmitted from the transmitter to the receiver during the gas filling from the gas station into the fuel tank, according to a state quantity regarding an interior of the fuel tank.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of InternationalApplication No. PCT/IB2011/000069, filed Jan. 18, 2011, and claims thepriority of Japanese Application No. 2010-018248, filed Jan. 29, 2010,the content of both of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a gas filling system that fills gas from a gasstation into, for example, a vehicle-mounted fuel tank, and also relatesto a vehicle equipped with such a fuel tank.

2. Description of the Related Art

Known gas stations as mentioned above include a hydrogen station thatfills hydrogen gas into a hydrogen tank of a fuel cell vehicle (see, forexample, Japanese Patent Application Publication No. 2005-069327(JP-A-2005-069327)) and Japanese Patent Application Publication No.2007-321572 (JP-A-2007-321572)). In Japanese Patent ApplicationPublication No. 2005-069327 (JP-A-2005-069327), the vehicle and thehydrogen station are electrically connected via an adaptor, andinformation about the maximum service pressure of the hydrogen tank ofthe vehicle is grasped at a hydrogen station side in order to controlhydrogen filling so that the maximum service pressure will not beexceeded.

While hydrogen is being filled, it is desirable to monitor thetemperature and the pressure in the hydrogen tank which rise inassociation with the hydrogen filling. In conjunction with this respect,consideration has been given to a construction in which, through the useof a communication equipment, signals regarding the temperature and thelike in the fuel tank are sent from the vehicle side and the hydrogenstation as need arises, and the hydrogen station automatically stops thehydrogen filling before the allowable temperature (reference value) ofthe hydrogen tank is exceeded (see, Japanese Patent ApplicationPublication No. 2007-321572 (JP-A-2007-321572)).

By the way, the hydrogen filling sometimes requires a long time,depending on conditions. For example, during the daytime under a blazingsun, the hydrogen tank is exposed to an environment whose temperature ishigher than normal temperature. If, in view of this situation, thehydrogen filling is performed at slower filling speed than at normaltemperature so that the temperature of the hydrogen tank will not exceedits allowable temperature, the filling time becomes long. If during sucha long-time filling, data about, for example, temperature in thehydrogen tank, and the like, is transmitted from the vehicle side to thehydrogen station side as need arises, there is a possibility that theelectric power source of the vehicle, which is at rest, may lack power.

SUMMARY OF THE INVENTION

The invention provides a gas filling system and a vehicle that reducethe electric power consumed during the gas filling.

A gas filling system in accordance with a first aspect of the inventionincludes: a vehicle having a fuel tank, a transmitter, and a controldevice that is connected to the transmitter; and a gas station having areceiver that receives a signal from the transmitter, wherein thecontrol device changes a transmission cycle of the signal that istransmitted from the transmitter to the receiver during gas filling fromthe gas station to the fuel tank, according to a state quantityregarding an interior of the fuel tank.

A vehicle in accordance with a second aspect of the invention includes:a fuel tank into which gas is filled from a gas station that has areceiver; a transmitter; and a control device that is connected to thetransmitter, and that changes a transmission cycle of a signaltransmitted from the transmitter to the receiver during the gas fillingfrom the gas station to the fuel tank, according to a state quantityregarding an interior of the fuel tank.

According to the first and second aspects of the invention, the signaltransmission cycle used during the gas filling is not fixed, but ischanged according to a state quantity regarding the interior of the fueltank. Due to this construction, for example, in the case where theinterior of the fuel tank has such a state quantity that the fillingtime will be long, selective use of a long transmission cycle willreduce the electric power needed for the transmission from thetransmitter in a single operation of gas filling as a whole. Hence, theelectric power consumption during gas filling can be reduced.

In the first and second aspect of the invention, the state quantityregarding the interior of the fuel tank may include temperature andpressure in the fuel tank, and if the temperature in the fuel tank isgreater than or equal to a first threshold value and the pressure in thefuel tank is less than or equal to a second threshold value, the controldevice may make the transmission cycle longer than if the temperature inthe fuel tank is less than the first threshold value or if the pressurein the fuel tank is greater than the second threshold value.

According to this construction, in the former case, in which the fillingtime will be longer than in the latter case, a longer transmission cyclecan be used to reduce the electric power consumption during the gasfilling. In particular, since the temperature and the pressure in thefuel tank are both compared with their respective threshold values, thestate in the fuel tank can be precisely grasped, so that the length ofthe transmission cycle can be appropriately determined.

It is to be noted herein that the first threshold value and the secondthreshold value each vary depending on the kinds of gas. In an examplecase where hydrogen gas is filled, the first threshold value is 60° C.,and the second threshold value is 2 MPa.

The vehicle may further include: a temperature sensor that detects thetemperature in the fuel tank; a pressure sensor that detects thepressure in the fuel tank, and the temperature in the fuel tank that iscompared with the first threshold value may be the temperature that thetemperature sensor detects before the gas filling starts, and thepressure in the fuel tank that is compared with the second thresholdvalue may be the pressure that the pressure sensor detects before thegas filling starts.

According to this construction, the length of the signal transmissioncycle during gas filling is determined on the basis of the temperatureand the pressure in the fuel tank which are grasped prior to the startof gas filling. This makes it possible to use a long signal transmissioncycle from the start of gas filling, so that it becomes possible tofurther reduce the electric power consumption.

The signal transmitted from the transmitter to the receiver during thegas filling may include detection information about the temperature andthe pressure in the fuel tank that the temperature sensor and thepressure sensor detect during the gas filling.

According to this construction, it is possible to detect the temperatureand the pressure in the fuel tank during the gas filling at the side ofthe gas station while restraining the electric power consumption neededfor the transmission performed by the transmitter.

The gas station may have a station-side control device that is connectedto the receiver, and the station-side control device may control the gasfilling into the fuel tank based on the detection signal that thereceiver receives.

According to this construction, at least one condition in the gasfilling suitable to the pressure and the temperature in the fuel tankduring the gas filling, for example, at least one of the filling speedand the amount of filling, can be changed.

In the foregoing construction, during the gas filling, if the receiverdoes not receive the signal from the transmitter during a predeterminedcycle, the station-side control device may determine that a transmissionerror has occurred, and the control device may set the transmissioncycle at less than half of the predetermined cycle.

According to this construction, it becomes possible to perform a processin terms of control in which it is determined that there is noabnormality occurring in the transmitter despite actual occurrence of atransmission error if the occurrence of the transmission error is thefirst occurrence, even in the case where a long transmission cycle isused.

The vehicle may have an electricity storage device that supplieselectric power to the temperature sensor, the pressure sensor, thetransmitter and the control device.

Since measures are provided to reduce the electric power consumptionduring the gas filling as mentioned above, the power shortage of theelectricity storage device during gas filling can be restrained. Thisrestrains, for example, occurrence of an event that the temperaturesensor or the like cannot input information.

The control device may use a first transmission cycle if an elapsed timefollowing start of the gas filling is less than or equal to a thirdthreshold value, and the control device may use a second transmissioncycle that is longer than the first transmission cycle if the elapsedtime exceeds the third threshold value.

According to this construction, in the case of a long-time gas fillingthat lasts longer than the third threshold value, the electric powerconsumption during gas filling can be reduced.

The transmitter and the receiver may be infrared communicationinstruments.

This construction reduces the electric power consumption during the gasfilling for which infrared communication is used.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, advantages, and technical and industrial significance ofthis invention will be described below with reference to theaccompanying drawings, in which like numerals denote like elements, andwherein:

FIG. 1 is a schematic diagram of a gas filling system in accordance withan embodiment of the invention;

FIG. 2 is a construction diagram of a gas filling system in accordancewith the embodiment of the invention;

FIG. 3 is a flowchart showing an operation procedure that a gas fillingsystem in accordance with the embodiment of the invention performsbefore starting filling gas;

FIG. 4 is a flowchart showing an operation procedure of determining atransmission cycle in accordance with a first modification of theembodiment of the invention; and

FIG. 5 is a flowchart showing an operation procedure of determining atransmission cycle in accordance with a second modification of theembodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will be described hereinafter withreference to the drawing. The following description will be made inconjunction with an example of a gas filling system in which hydrogengas is filled from a hydrogen station into a fuel tank of a fuel cellvehicle equipped with a fuel cell system. Incidentally, the fuel cellsystem includes a fuel cell that generates electricity byelectrochemical reaction between a fuel gas (e.g., hydrogen gas) and anoxidizing gas (e.g., air). Besides, the filling of hydrogen gas is onemanner of supplying hydrogen gas from the hydrogen station into the fueltank.

As shown in FIG. 1, a gas filling system 1 includes, for example, ahydrogen station 2 as a gas station, and a vehicle 3 that is suppliedwith hydrogen gas from the hydrogen station 2.

As shown in FIG. 2, the vehicle 3 includes a fuel tank 30, a receptacle32, a pressure sensor 36, a temperature sensor 38, a display device 42,a communication instrument 44, and a control device 46. The fuel tank 30is a fuel gas supply source for the fuel cell, and, for example, is ahigh-pressure tank that is capable of storing hydrogen gas at 35 MPa or70 MPa. In the case where a plurality of fuel tanks 30 are mounted inthe vehicle 3, the fuel tanks 30 are connected in parallel to the fuelcell. The hydrogen gas in the fuel tank 30 is supplied to the fuel cell50 through a supply channel 52. On the other hand, the supply ofhydrogen gas to the fuel tank 30 is carried out by the hydrogen station2 releasing hydrogen gas into a filling channel 34 through a receptacle32. The filling channel 34 is made up of a gas piping provided outsidethe fuel tank 30, and a channel portion that is provided in a valveassembly (not shown) that is attached to an opening portion of the fueltank 30. Besides, the filling channel 34 is provided with a check valve35 for restraining reverse flow of the hydrogen gas.

The pressure sensor 36 detects the pressure of the hydrogen gas releasedfrom the hydrogen station 2, and is provided in the filling channel 34.For example, the pressure sensor 36 is provided in the foregoing gaspiping that is provided at a downstream side of the check valve 35 andthat is immediately upstream of the fuel tank 30, and detects a pressurethat substantially reflects the pressure of the hydrogen gas within thefuel tank 30 (hereinafter, referred to as “tank pressure”). Thetemperature sensor 38 is provided in a channel portion in the valveassembly, and is disposed within the fuel tank 30. The temperaturesensor 38 detects a temperature that reflects the temperature ofhydrogen gas within the fuel tank 30 (hereinafter, referred to as “tanktemperature”). Incidentally, in other embodiments, the pressure sensor36 may also be disposed within the fuel tank 30. Besides, the positionin the fuel tank 30 at which the temperature sensor 38 is disposed isnot particularly limited as long as the position allows the tanktemperature to be substantially detected. It is preferable that thetemperature sensor 38 be provided near a blowout opening that leadshydrogen gas into the fuel tank 30.

The display device 42 is able to be used, for example, as a portion of acar navigation system, and displays various kinds of information in itsdisplay screen. The communication instrument 44 is provided forcommunicating with the hydrogen station 2, and, for example, as acommunication interface for wireless communication such as an infraredcommunication and the like. The communication instrument 44 is built inthe receptacle 32 or is fixed within a lidded box of the vehicle 3 so asto be capable of communication when a filling nozzle 12 of the hydrogenstation 2 is connected to the receptacle 32.

The control device 46 is constructed as a microcomputer that has thereina CPU, a ROM and a RAM. The control device 46 controls the vehicle 3.The CPU executes desired computations according to control programs soas to perform various processes and controls, such as changing thetransmission cycle of the communication instrument 44. The ROM storescontrol programs and control data that are processed by the CPU. The RAMis used mainly as various workspaces for control processes. The controldevice 46 is connected to the pressure sensor 36, the temperature sensor38, a display device 42, a communication instrument 44, etc., and sends,for example, information detected by the pressure sensor 36 and thetemperature sensor 38, to the hydrogen station 2 by using thecommunication instrument 44.

A high-voltage DC/DC converter 54 that controls the output voltage ofthe fuel cell 50 is connected to the fuel cell 50. Various high-voltageaccessories 56 that are used for the operation of the fuel cell 50 areelectrically connected between the fuel cell 50 and the high-voltageDC/DC converter 54. The high-voltage accessories 56 are accessories thatneed high voltage (e.g., a voltage above 12 V), for example, an aircompressor that pressure-feeds an oxidizing gas to the fuel cell 50, ahydrogen pump that supplies an hydrogen off-gas to the fuel cell 50 in acirculating manner. The electricity storage device 58 is achargeable-dischargeable secondary cell that functions as a high-voltageelectricity storage device. The electricity storage device 58 isconnected to, for example, a traction motor of the vehicle 3 via thehigh-voltage DC/DC converter 54, in parallel with the fuel cell 50.

A low-voltage DC/DC converter 60 is electrically connected between thehigh-voltage DC/DC converter 54 and the electricity storage device 58.The low-voltage DC/DC converter 60 lowers the voltage of a portion ofthe direct-current power of a high-voltage circuit side, and suppliesthe lowered-voltage power to a low-voltage circuit side. Thelowered-voltage direct-current power is partially used to charge thelow-voltage battery 62, and is partially used as power to drivelow-voltage accessories 64. The low-voltage battery 62 functions as anelectricity storage device of low voltage (e.g., 12 V), and is asecondary cell that is represented by, for example, a nickel metalhydride cell, a lithium ion cell. The low-voltage accessories 64 arevarious appliances that are driven at low voltage, and are differentfrom the high-voltage accessories 56. What are regarded as thelow-voltage accessories 64 are, for example, the pressure sensor 36, thetemperature sensor 38, the display device 42, the communicationinstrument 44, etc. The low-voltage accessories 64 and the controldevice 46 are also driven when supplied with electric power from thelow-voltage battery 62 as a power supply source. For example, while thevehicle 3 is in an ignition-off state (hereinafter, referred to as“IGOFF”), the fuel cell 50 does not generate electricity, and thereforethe power for the low-voltage accessories 64 and the control device 46is supplied from the low-voltage battery 62.

The hydrogen station 2 includes a control device 5 that controls variousappliances and the like that are provided at the hydrogen station 2, acommunication instrument 6 for communicating with the vehicle 3, adisplay device 7 that displays various kinds of information in itsdisplay screen, and an outside air temperature sensor 8 that detects theoutside air temperature at the location where the hydrogen station 2 isinstalled. The communication instrument 6 is of a type that is pursuantwith the communication instrument 44 of the vehicle 3, and sends andreceives various kinds of information to and from the communicationinstrument 44. The display device 7 displays information such as thefilling speed (filling flow rate) and the filling amount during thefilling operation, and the like. Besides, the display screen of thedisplay device 7 is equipped with an operation panel on which anoperating person or a user (hereinafter, collectively referred to as“user”) is allowed to input a desired filling condition. That is, theuser is allowed to designate a complete filling of the tank (completefilling), a desired filling amount, a desired amount of money to be paidfor a single operation of filling, etc., as desired filling conditions,via the operation panel of the display device 7. Incidentally, in otherembodiments, it is also permissible to adopt a construction that is ableto receive filling conditions input from a user by using a devicedifferent from the display device 7.

Besides, the hydrogen station 2 has a cluster of tanks (a gas supplysource) 11 that stores hydrogen gas, a filling nozzle 12 that releaseshydrogen gas toward the fuel tank 30 mounted in the vehicle 3, and a gaschannel 13 that connects the cluster of tanks 11 and the filling nozzle12. The filling nozzle 12 is also called filling coupling, and isconnected to the receptacle 32 of the vehicle 3 when hydrogen gas isfilled into the vehicle 3. The filling nozzle 12 and the receptacle 32form a connecting unit that connects the hydrogen station 2 and the fueltank 30. Besides, the filling nozzle 12 is provided with a pressuresensor 9 and a temperature sensor 10 that detect the pressure and thetemperature of hydrogen gas that the hydrogen station 2 supplies to thefuel tank 30. Due to the provision of these sensors 9 and 10 on thefilling nozzle 12, the actual pressure and the actual temperature of thehydrogen that is actually supplied from the hydrogen station 2 to thefuel tank 30 can be acquired by a simple construction. Besides, it ispreferable that the temperature sensor 10 be provided at a distal end ofthe filling nozzle 12 (a fuel tank 30-side portion of the filling nozzle12).

The gas channel 13 is provided with a compressor 14, a pressureaccumulator 15, a pre-cooler 16, a flow control valve 17, a flow meter18 and a dispenser 19. The compressor 14 compresses hydrogen gas fromthe cluster of tanks 11, and discharges it. The pressure accumulator 15stores hydrogen gas whose pressure has been raised to a predeterminedpressure by the compressor 14. The pre-cooler 16 cools the hydrogen gasfrom the pressure accumulator 15 whose temperature is approximatelyequal to room temperature to a predetermined low temperature (e.g., −20°C. or −40° C.). The flow control valve 17 is an electrically drivenvalve, and adjusts the amount of flow of hydrogen gas from the pressureaccumulator 15 in accordance with a command from the control device 5.Due to this, the filling flow rate (filling speed) of hydrogen gas tothe fuel tank 30 is controlled. This controlled filling flow rate ismeasured by the flow meter 18. In response to a result of themeasurement, the control device 5 performs a feedback control of theflow control valve 17 so as to achieve a desired filling flow rate.Incidentally, it is also possible to use a flow rate control deviceother than the flow control valve 17. The dispenser 19 is sends outhydrogen gas to the filling nozzle 12. For example, if a trigger leverof the filling nozzle 12 is pulled, the dispenser 19 is actuated tobecome able to discharge hydrogen gas from the filling nozzle 12 towardthe fuel tank 30. Incidentally, although not shown in the drawings, ashutoff valve that opens the gas channel 13 during the filling operationis provided in the pressure accumulator 15 or at a downstream side ofthe pressure accumulator 15.

The control device 5 is constructed as a microcomputer that has thereina CPU, a ROM and a RAM. The CPU executes desired computations accordingto control programs so as to perform various processes and controls. TheROM stores control programs and control data that are processed by theCPU. The RAM is used mainly as various workspaces for control processes.The control device 5 is electrically connected to the communicationinstrument 6, the display device 7, the outside air temperature sensor8, the pressure sensor 9, the temperature sensor 10, the flow controlvalve 17, the flow meter 18, the pressure accumulator 15, etc., whichare connected by a control line shown by a dashed one-dotted line inFIG. 2. For example, the control device 5 recognizes the pressure andthe temperature that the pressure sensor 36 and the temperature sensor38 detect, as the pressure and the temperature in the fuel tank 30(i.e., the tank pressure and the tank temperature) of the vehicle 3, andaccordingly controls the filling of hydrogen gas. Specifically, thecontrol device 5 controls the degree of opening of the flow controlvalve 17 on the basis of the information regarding the tank pressure andthe tank temperature of the vehicle 3 side which the control device 5receives from the communication instrument 6. Besides, the controldevice 5 sends information that is obtainable at the hydrogen station 2to the communication instrument 44 of the vehicle 3, by using thecommunication instrument 6.

Thus, the communication instruments 6 and 44 function as receivers andtransmitters that receive and transmit signals that include variouskinds of information from and to each other. As the communicationinstruments 6 and 44, it is possible to use infrared communicationinstruments that each include a transmission element and a receptionelement. The transmission element and the reception element of eachcommunication instrument may be constructed of, for example, an infraredlight-emitting diode and a photodiode, respectively.

In the gas filling system 1 described above, when hydrogen gas is to befilled into the vehicle 3, the filling nozzle 12 is firstly connected tothe receptacle 32, and then the dispenser 19 is actuated while theconnection therebetween is maintained. Then, hydrogen gas is releasedfrom the filling nozzle 12 toward the fuel tank 30, and is thereforefilled into the fuel tank 30. In the gas filling system 1 of thisembodiment, before the filling is started, the state quantity regardingan interior of the fuel tank 30 is grasped. If the state quantitysatisfies a predetermined condition, the cycle of the transmission fromthe vehicle 3 to the communication instrument 44 of the hydrogen station2 is elongated (i.e., the next transmission timing is delayed). In thismanner, the electric power consumption during the gas filling isminimized.

Next, an operation procedure of determining the transmission cycle ofthe communication instrument 44 in the gas filling system 1 will bedescribed with reference to FIG. 3. The procedure shown in FIG. 3 isexecuted before the filling of hydrogen gas from the hydrogen station 2into the fuel tank 30 is started.

Firstly, the electric power source of the control device 46 of thevehicle 3 is turned on (step S1). This is carried out by supplyingelectric power from the low-voltage battery 62 to the control device 46.Examples of the trigger of turning on the electric power source of thecontrol device 46 includes detecting that the operation of connectingthe filling nozzle 12 and the receptacle 32 has been performed, by meansof a sensor (not shown). It is also permissible to detect that a fuelcover of a lidded box of the vehicle 3 has been opened, by means of asensor, through the use of a method different from the foregoing method.When the electric power source of the control device 46 is turned on,the pressure sensor 36, the temperature sensor 38 and the communicationinstrument 44 are activated. The activation of these devices and thelike is carried out by the supply of electric power from the low-voltagebattery 62.

Then, after the activation of the pressure sensor 36 and the temperaturesensor 38 is completed, a tank pressure P₁ and a tank temperature T₁(hereinafter, sometimes referred to as “initial tank pressure” and“initial tank temperature”, respectively) are input as state quantitiesof the fuel tank 30 occurring before the filling starts. Informationabout the tank pressure P₁ and the tank temperature T₁ that are input istemporarily stored into, for example, the RAM of the control device 46.On the other hand, simultaneously with or prior or subsequently to thecompletion of the activation of the pressure sensor 36 and thetemperature sensor 38, the activation of the communication instrument 44is completed. At this time, if the operation of connecting the fillingnozzle 12 and the receptacle 32 has been completed, a state in whichwireless communication is possible between the hydrogen station 2 andthe vehicle 3 is established.

Next, in step S2, it is determined whether or not the tank temperatureT₁ is greater than or equal to a threshold value T_(th). Thisdetermination is carried out by the control device 46. The thresholdvalue T_(th) is determined beforehand, by factoring in the filling time,and is stored beforehand in the ROM of the control device 46.

Concretely, through an evaluation test or a simulation performedbeforehand, it is possible to grasp the approximate lengths of thefilling time corresponding to various tank temperatures and various tankpressures. For example, through a prior evaluation, it has beenascertained that when the tank temperature of a fuel tank is greaterthan or equal to 60° C. and the tank pressure thereof is less than orequal to 2 MPa, the filling time required is greater than or equal to 40minutes. The filling time tends to be longer the higher the tanktemperature. Therefore, when the tank temperature is about normaltemperature, a long filling time that is greater than or equal to 40minutes is not required. In view of what has been described above, thethreshold value T_(th) in this embodiment is set at a tank temperaturethat has been ascertained to require a long filling time (e.g., 40minutes or more) through a prior evaluation or the like. An example ofthe threshold value T_(th) is 60° C.

However, the threshold value T_(th) varies depending on thecharacteristics (heat dissipation characteristic) of the fuel tank 30and also on the reference temperature (allowable temperature) of thefuel tank 30, the cooling capability of the pre-cooler 16, etc. That is,differences in these factors vary the filling time. For example, theheat dissipation characteristic of the fuel tank 30 is better in thecase where aluminum is used as a liner of the fuel tank 30 than in thecase where a resin (polyethylene or the like) is used as the liner.Therefore, in the former case, it is possible to increase the thresholdvalue T_(th). Besides, the rise of the tank temperature caused by thefilling can be made less the lower the temperature of hydrogen gas thatcan be achieved by the pre-cooler 16. Therefore, it is also possible tomake the threshold value T_(th) larger the higher the cooling capabilityof the pre-cooler 16. Therefore, while the threshold value T_(th) instep S2 can be a fixed value (60° C. as in the foregoing example), thethreshold value Tth can also be varied on the basis of a characteristicof the fuel tank 30 or the like. Incidentally, it should be apparentthat in the case where the gas to be filled in is a gas that isdifferent in kind from hydrogen gas, the threshold value T_(th) used isalso different from that used in the case where the gas to be filled inis hydrogen gas.

If it is determined in step S2 that the tank temperature T₁ is less thanthe threshold value T_(th) (NO in step S2), it is considered that thefilling time required is not very long. Therefore, the control device 46determines that a transmission cycle T_(A) is to be used, without takingthe tank pressure P₁ into account (step S3). On the other hand, if thetank temperature T₁ is higher than or equal to the threshold valueT_(th) (YES in step S2), it is considered that a long filling time willbe required. Therefore, the control device 46 compares the tank pressureP₁ with the threshold value P_(th) (step S4).

The threshold value P_(th), similar to the threshold value T_(th), isdetermined beforehand by taking the filling time into account, and isstored beforehand in the ROM of the control device 46. In this case, thefilling time tends to be long the lower the tank pressure. The thresholdvalue P_(th) in this embodiment is set at a tank pressure that has beenascertained to require a long filling time (e.g., 40 minutes or more)through a prior evaluation or the like. An example of the thresholdvalue P_(th) is 2 MPa. It is to be noted herein that the threshold valueP_(th), similar to the threshold value T_(th), may be a fixed value, ormay also be varied on the basis of characteristics (heat dissipationcharacteristic) of the fuel tank 30, the reference temperature(allowable temperature) of the fuel tank 30, or the cooling capabilityof the pre-cooler 16, etc.

If in step S4 it is determined that the tank pressure P₁ is greater thanthe threshold value P_(th) (NO in step S4), it is considered that thefilling time will not be long, and therefore it is determined to use asignal transmission cycle T_(A) (step S3). On the other hand, if thetank pressure P₁ is less than or equal to the threshold value P_(th)(YES in step S4), it is considered that the filling time will be long.Therefore, the control device 46 determines to use a signal transmissioncycle T_(B) that is longer than the transmission cycle T_(A) (step S5).

The transmission cycles T_(A) and T_(B) will be described. The term“transmission cycles T_(A) and T_(B)” refers to a cycle period of asignal that the communication instrument 44 transmits to thecommunication instrument 6. That is, the time duration from when thecommunication instrument 44 transmits a signal to the communicationinstrument 6 to when the communication instrument 44 transmits the nextsignal to the communication instrument 6 is the transmission cycle. Thetransmission cycles T_(A) and T_(B) are used for the communicationbetween the communication instrument 44 and the communication instrument6 during the filling, and are stored beforehand in a storage portionsuch as the ROM of the control device 46 or the like. In an example, thetransmission cycle T_(A) is 100 ms, and the transmission cycle T_(B),which is longer than the transmission cycle T_(A), is 200 ms, 300 ms or400 ms. However, if there is a standard of the maximum length of thetransmission cycle during the filling, the transmission cycles T_(A) andT_(B) are set within a range of the cycle that satisfies the standardmaximum length and that does not affect the filling.

It is preferable to determine whether or not a transmission error of thecommunication instrument 44 has occurred. As an index for thedetermination, it is advisable to use the presence/absence of receptionof a signal from the communication instrument 6 during a fixed period.For example, if during a fixed period (predetermined cycle) of 500 ms,the communication instrument 6 does not receive a signal from thecommunication instrument 44, it can be determined that a transmissionerror of the communication instrument 44 has occurred. Thisdetermination can be performed by the control device 5 during thefilling.

Therefore, in the case where the control device 5 has a reference fordetermining whether a transmission error of the communication instrument44 has occurred, it is preferable to set the transmission cycles T_(A)and T_(B) at less than half of the predetermined cycle period that isused according to the foregoing reference. Concretely, in the foregoingexample, in the case where the predetermined cycle period is 500 ms, itis preferable that the transmission cycle T_(B) be set at 200 ms, whichis less than 250 ms. This setting makes it possible for the controldevice 5 to perform a process in terms of control in which atransmission error, if occurring for the first time, is assumed to be nooccurrence of abnormality in the communication instrument 44. Thissetting is particularly useful in the case where the reliability ofcommunication is low. Incidentally, in the case where the reliability ofcommunication is high, the transmission cycle T_(B) may be set at a halfor more of the predetermined cycle period.

After the transmission cycle T_(A) or T_(B) is determined (step S3 orS5), the communication during the filling is performed at the determinedtransmission cycle. More specifically, after the determination of thetransmission cycle, information about the initial tank pressure and theinitial tank temperature is transferred to the control device 5 of thehydrogen station 2. Next, the control device 5 looks up the initial tankpressure and the initial tank temperature that are received in a fillingspeed map, and starts the filling so as to achieve a filling speed thatcorresponds to the initial tank pressure and temperature.

During the filling, the tank pressure and the tank temperature are inputas needed, and a signal that contains information about the tankpressure and the tank temperature that are input is transmitted from thecommunication instrument 44 to the communication instrument 6 at thedetermined transmission cycle T_(A) or T_(B). Owing to this, the controldevice 5 monitors the tank pressure and the tank temperature during thefilling. Then, the control device 5 looks up the tank pressure and thetank temperature that the control device 5 monitors in the filling speedmap, and controls the degree of opening of the flow control valve 17 soas to change the filling speed according to need. Incidentally, duringthe filling, the vehicle 3 is in an IGOFF state, so that the electricpower for the communication instrument 44 is supplied by the low-voltagebattery 62.

As the filling operation completes a filling that satisfies a desiredfilling condition that the user has designated, the supply of hydrogengas to the fuel tank 30 is stopped, and the filling ends. After that,the filling nozzle 12 is detached from the receptacle 32, and the powersource of the pressure sensor 36, the temperature sensor 38 and thecommunication instrument 44 is turned off, that is, the supply ofelectric power thereto from the low-voltage battery 62 ends. Then, theelectric power source of the control device 46 is also turned off.

Operation and effects of the foregoing embodiment will be described.During the communication-based filling of the fuel tank 30, the electricpower source used for the communication instrument 44 and the like inthe vehicle 3 is the low-voltage battery 62. Therefore, if thetransmission cycle T_(A), which is relatively short, is used during thefilling whose filling time is long, there arises possibility of powershortage of the low-voltage battery 62.

In this embodiment, in the case where it is determined from the initialtank temperature and the initial tank pressure that the filling timewill be long, the transmission cycle T_(B), which is relatively long, isused during the filling. Therefore, during the entire single operationof filling, the electric power needed for the communication via thecommunication instrument 44 decreases, so that the electric powerconsumption during the filling can be reduced. Therefore, it is possibleto restrain the low-voltage battery 62 from entering a so-called deadstate.

Incidentally, although in the foregoing embodiment, a transmission cycleis determined before the filling is started, it is also possible toperform steps S2 to S4 in FIG. 3 after the filling is started. In thiscase, the length of the transmission cycle is determined from the statequantity (tank temperature, tank pressure) regarding the interior of thefuel tank 30 after the filling is started, and is then used.

MODIFICATIONS

Modifications of the foregoing embodiment will be described. Thefollowing modifications are applicable to each other.

First Modification

A first modification shown in FIG. 4 is different from the foregoingembodiment mainly in that the transmission cycles T_(A) and T_(B) aredetermined on the basis of the elapsed time in the filling.

Firstly, after the same process as in step S1 in FIG. 3 is performed(step S11), a filling speed corresponding to the initial tank pressureand the initial tank temperature is selected from a filling speed map,and the filling of the fuel tank 30 is accordingly started (step S12).Next, the elapsed time following the start of the filling (hereinafter,referred to as “elapsed filling time”) is measured by a timer (notshown), and it is checked whether or not the elapsed filling time isgreater than a predetermined threshold value (third threshold value)(step S13). This checking can be performed by the control device 46 ofthe vehicle 3. The predetermined threshold value can be arbitrarily set;for example, it can be set at 20 minutes or 40 minutes.

If in step S13 it is checked that the elapsed filling time is less thanor equal to the predetermined threshold value (NO in step S13), it isdetermined to use the transmission cycle T_(A), and the filling isaccordingly continued (step S14). On the other hand, if the elapsedfilling time is longer than the predetermined threshold value (YES instep S13), it is determined to use the transmission cycle T_(B), whichis longer than the transmission cycle T_(A), and the filling isaccordingly continued (step S15). Therefore, according to the firstmodification, in the case of a long-time filling whose filling timeexceeds the predetermined threshold value, the electric powerconsumption during the filling can be reduced.

Incidentally, in step S13, it is also permissible to compare anactivation time of the communication instrument 44 with a thresholdvalue (e.g., 20 minutes or 40 minutes). In this case, when the fillingis started in step S12, the hydrogen station 2 has not grasped theinitial tank pressure nor the initial tank temperature yet, andtherefore the filling is started at a filling speed that is set bytaking safety into account. For example, the filling is started by usingas an initial tank pressure the pressure hydrogen gas supplied from thehydrogen station 2 (e.g., detected at the nozzle 12) or a higherpressure, and using as an initial tank temperature the outside airtemperature (a value detected by the outside air temperature sensor 8)or a temperature below the detected value.

The first modification can be performed independently of the operationprocedure shown in FIG. 3, or can also be incorporated into theprocedure shown in FIG. 3. In the latter case, the process of steps S12to S15 shown in FIG. 15 is incorporated after the process of steps S3and S5 shown in FIG. 3.

Second Modification

A second modification shown in FIG. 5 is different from the foregoingembodiment mainly in that the transmission cycles T_(A) and T_(B) aredetermined on the basis of the voltage of the low-voltage battery 62,which is a battery for accessories.

Firstly, in step S21, the same process as in step S1 in FIG. 3 isperformed. Next, in step S22, the voltage of the low-voltage battery 62(the state of charge thereof) is detected by an SOC sensor (not shown),and it is checked whether or not the detected voltage of the low-voltagebattery 62 is less than or equal to a predetermined threshold value(step S22). This checking can be performed by the vehicle 3-side controldevice 46. The predetermined threshold value for use for comparison instep S22 can be arbitrarily set; for example, it can be set at a voltagethat corresponds to 20% or 30% of the full voltage (full state orcharge).

If in step S22 it is checked that the voltage of the low-voltage battery62 is greater than the predetermined threshold value (NO in step S22),it is determined that the dead battery will not occur during thefilling, and it is determined to use the transmission cycle T_(A) (stepS23). On the other hand, if the voltage of the low-voltage battery 62 isless than or equal to the predetermined threshold value (YES in stepS22), it is determined that the dead battery will occur during thefilling, and it is determined to use the transmission cycle T_(B), whichis longer than the transmission cycle T_(A). Therefore, according to thesecond modification, the electric power consumption during the fillingcan be reduced.

The second modification can be performed independently of the procedureshown in FIG. 3, and can also be incorporated into the procedure shownin FIG. 3. In the latter case, the procedure shown in FIG. 3 isperformed before the filling is started, and during the filling, theprocess of steps S22 to S24 shown in FIG. 5 is performed by monitoringthe voltage of the low-voltage battery 62.

Third Modification

It is also possible to adopt a construction in which the functions ofthe vehicle 3-side control device 46 is to two control devices, and inwhich both control devices receive electric power from the low-voltagebattery 62. For example, in a construction in which a fuel-cell controldevice for use for the electricity generation control of the fuel cell50 and a filling control device for use for the control ofcommunication-based filling are used, it suffices that the fillingcontrol device is equipped with functions needed for the foregoingcommunication-based filling which are performed by the control device 46in the foregoing embodiment (functions that are needed in order toexecute the procedures shown in FIGS. 3 to 5). In this construction, theprocess of “turning on the power source of a vehicle-side controldevice” which is shown in steps S1, S11 and S21 in FIGS. 3 to 5 isperformed only for the filling control device, and does not need to beperformed for the fuel-cell control device.

The gas filling system and the vehicle of the invention can be appliednot only to hydrogen gas, but also to other fuel gases such as naturalgas and the like. Besides, the invention is applicable not only towheeled vehicles but also to other mobile units equipped with fuel tanksas an object of the filling of a fuel gas from outside, such asaircrafts, ships and boats, robots, etc.

The invention claimed is:
 1. A gas filling system comprising: a vehiclehaving a fuel tank, a transmitter, and a vehicle-side control devicethat is connected to the transmitter; and a gas station having areceiver that receives a signal from the transmitter, wherein thevehicle-side control device changes a transmission cycle of the signalthat is transmitted from the transmitter to the receiver during gasfilling from the gas station to the fuel tank that is a time durationfrom when the transmitter transmits a signal to the receiver to when thetransmitter transmits the next signal to the receiver, according to astate quantity regarding an interior of the fuel tank.
 2. The gasfilling system according to claim 1, wherein the state quantityregarding the interior of the fuel tank includes temperature andpressure in the fuel tank, and if the temperature in the fuel tank isgreater than or equal to a first threshold value and the pressure in thefuel tank is less than or equal to a second threshold value, thevehicle-side control device makes the transmission cycle longer than ifthe temperature in the fuel tank is less than the first threshold valueor if the pressure in the fuel tank is greater than the second thresholdvalue.
 3. The gas filling system according to claim 2, wherein thevehicle has a temperature sensor that detects the temperature in thefuel tank and a pressure sensor that detects the pressure in the fueltank, and the temperature in the fuel tank that is compared with thefirst threshold value is the temperature that the temperature sensordetects before the gas filling starts, and the pressure in the fuel tankthat is compared with the second threshold value is the pressure thatthe pressure sensor detects before the gas filling starts.
 4. The gasfilling system according to claim 3, wherein the signal transmitted fromthe transmitter to the receiver during the gas filling includesdetection information about the temperature and the pressure in the fueltank that the temperature sensor and the pressure sensor detect duringthe gas filling.
 5. The gas filling system according to claim 4, whereinthe gas station has a station-side control device that is connected tothe receiver, and the station-side control device controls the gasfilling into the fuel tank based on the detection signal that thereceiver receives.
 6. The gas filling system according to claim 3,wherein the vehicle has an electricity storage device that supplieselectric power to the temperature sensor, the pressure sensor, thetransmitter and the vehicle-side control device.
 7. The gas fillingsystem according to claim 2, wherein the gas station has a station-sidecontrol device that is connected to the receiver, and, during the gasfilling, if the receiver does not receive the signal from thetransmitter during a predetermined cycle, the station-side controldevice determines that a transmission error has occurred, and thevehicle-side control device sets the transmission cycle at less thanhalf of the predetermined cycle.
 8. The gas filling system according toclaim 2, wherein the vehicle-side control device uses a firsttransmission cycle as the transmission cycle if an elapsed timefollowing start of the gas filling is less than or equal to a thirdthreshold value, and the vehicle-side control device uses a secondtransmission cycle that is longer than the first transmission cycle asthe transmission cycle if the elapsed time exceeds the third thresholdvalue.
 9. The gas filling system according to claim 2, wherein thetransmitter and the receiver are infrared communication instruments.